Process of extracting copper from ore.



LAIST.

PROCESS OF EXTRACTING COPPER FROM ORE.

AlPLIGTIoN FILED 17110.16, 1912.

Press Ca kes. /c/d So/uf/m.

ATTORNEY.

'F'.REIDEBK LAIST, 0F ANLCDNDA, MUNTANA..

PROCESS 0F '.EXLMCTING COPPER ERM ORE.

remesa.,

Specication of .'Ictters Patent.

Patented Oct. 28, 1913.

Application aled :December 1f6,` 1912. Serial No. 737,114.

To all whom il? may vconcern Be it known that I, FREDERICK lLAIsT, citizen of the United States, residing at Anaconda, in the county of Deerlodge and State of Montana, have invented certain new `and useful Improvements in Processes of Extracting Copper from Ure, of which the following is a full, clear, and exact description, reference beingr had to the accompanying drawings, 'forming a part hereof.

The present invention is speciically directed to the recovery of copper from low grade ores or tailings in which .the metal may be in the form of oxid, carbonate, silicate or sulfid, or in fact in any form capable of dissolving ina liquid from which it may be precipitated bytlie action of sulfureted hydrogen. ln the present embodiment of my invention the process likewise contemplates'the recovery .of any silver which may be associated with the copper, the object of the invention beingvto attain the recovery of these values with a minimum waste of both metal and of the solutions which enter into the chemical reactions inherent in the rocess. l 'While no .specific form of apparatus or combination of apparatus is necessarily identitied with my improved process it will be convenient to illustrate diagrammatica-lly at least the relation of the component parts comprising a plant in which the several reactions may be carried out. Such a vdiagram is illustrated in the accompanying drawing.

lf the ore is in a form other than the sulhd no specialV preliminary chemical treatment thereof is necessary as it can be attacked by a proper leaching solvent from which the metal may subsequently be precipitated by sulfureted hydrogen. lnasmuch as the sultid however, requires special preliminary treatment, particularly Where silver is associated with the copper, it is desirable thatthe details vof the process be set forth on the assumption that silver is present.

ln detail vthe invention may be described as follows, reference being hadin an incidental way to the diag-ram illustrated in the drawing.

The low Agrade ore or tailings (reduced to a size convenient for roasting) is lirstsubjected to apreliminary roast for the oxidation and partial elimination of the sulfur content, such preliminary roast being of an oxidizing character and conducted preferably in a multiple hearth Mcougal roast ing furnace, the details of which form the subjectanatter of an independent applicaf tion for patent. For convenience we shall assume that the furnace comprises six super posed heart-hs in the three upper ones ot' which the oxidizing roast is carried on. As a result of this oxidizing (or sultating) roast the copper suliid is converted into a probable mixture of copper oxid and copper sulfate, part of the silver sulid being converted into a .sulfate of silver, andthe iron (generally present) into a mixture of ferrous oxid and ferrous sulfate. The material thus subjected to an oxidizingf roast in the three upper hearths of the furnace drops' down and traverses the three bottom hearths, where it is subjected to a chloridizing roast by the addition thereto of a sutiicient quantity of common salt, (say one per cent, which however, is varied according to the character of the charge). ln this chloridizing action all the silver and some of the copper is converted into the chlorid, the chlorid of iron which is likewise formed being broken up into the oxid by the heat, and oxygen present. At this stage of the process the reactions are probably as follows:

Any unconverted copper sulfate isdis charged from the furnace with the silver chlorid and copper chlorid, .and with any iron oXid present in the cbloridized charge. ln the chloridizin'g roasting action some of the copper passes 0E ,as fumes of copper chlorid together with any fumes of hydro chloric acid which may be produced as a result of the. Ageneration of nascent chlorin gas due to the decomposition of thesalt. Such fumes are drafted fromthe lower set of chloridizing hearths by any form of eX- hauster and allowed to traverse an .absorption tower of any approved pattern where they are .absorbed by the water in the tower and returned to the leaching solution employed for dissolving the roasted and chloridized product. llt may be stated in passl ingr that to successfully carry on the chlorid izing roast a sufficient quantity of air should be admitted to the lower hearths of the furnace, for that purpose.

Upon the conclusion of the combined sulfating (oxidizing) and chloridizing roast, the material (calcine) is discharged from the bottom hearth of the furnace and conveyed to a leaching tank or tanks into which is conducted at the necessary rate of speed, a leaching solution composed of water with about five per cent'. of sulfuric acid (H2504) and ten per cent. of common salt (NaCl) (the solution containing incidentally as presently to be seen, certain amounts of iron and aluminum sulfates and chlorids as impurities due to the action of the wash solutions on the ore charge arid the absorption of similar impuritiesl by the water yin the absorption tower). The leaching solution dissolves the several metallic compounds present in the charge deposited in the leaching tank, thereby bringing about a mixed acid solution of copper chlorid,copper sulfate, silver chlorid, (and iron and aluminumsulfates and chlorids as impurities). The solution of the combined metals is then drained o or conducted from the leacliinr tank into a precipitating vat or tower into which is conducted sulfureted hydrogen gas (HZS) which precipitates the metals (copper and silver) as sulids as indicated by the following reactions- The sulfureted hydrogen does not of course, precipitate the iron or aluminum, these salts remaining permanent components of the solution. From the precipitating vat or tower the mixture of precipitates and solution is conducted to a settling tank from whichthe thickened precipitate (CUS and Ag2S) is conducted to a precipitate storage tank, the acid solution being conveyed to one of the leach solution containers and used for leaching fresh charges of ore. From the last reactions it will be seen that the acid (H2504, HC1) is ,regenerated and is thus used over again; but to prevent the building up of Iundue quantities of iron and aluminum., compounds which remain as permanent component parts of the liquid, the regenerated solution is split at the end of each cycle or operation, and a portion of the liquid is discarded, approximately ten per cent. being allowed to go to waste, and

ninety per cent. is returned for leaching fresh charges of ore. From the precipitate storage tank the `precipitates of copper sulid and silver sul'ld are conducted to a filter press, the press cakes being sent to the converter plant or smelter. The sulfureted hydrogen as a precipitant has the advantage over the majority of others in that it introduces no undesirable impurities into the solution. It has the advantage over electrolytic precipitation in thatthe plant outlay 1s much less, and its action is in no wise affected by ordinary impurities ldissolved from the ore by the acid solvent.

In carrying on my process I generate the sulfureted hydrogen by treating. iron matte or iron-copper matte with dilute sulfuric acid. The matte is made by smelting pyrite or pyrrhotite ore, preferably containing gold and silver values, in a reverberatory or blast furnace with the addition of necessary fluxes, thus forming a slag and a matte. This matte is chiefly suld of iron (F eS) and is readily decomposed by dilute sulfuric acid with the formation of sulfureted hydrogen and iron sulfate, thus In practice the matte drawn from the furnace together with the sulfuric acid is con-J tank or tanks) to wash the sand remaining` in the tank after the metallic salts have been dissolved out. The wash solution #5 after passing through the leaching tank is discharged into wash solution #4. From the latter the solution again passes through the leaching tank and discharges into wash solution #3. From this t-he solution passes through the leaching tank and discharges into leach solution #1. Likewise from leach solution #2 the li uid passes through the leaching tank and ischarges into leaching solution #1. The regenerated solution or acid solvent is discharged into leach solution #2, the solution from leach solution #l being availed of to dissolvel the main metal content' of the leaching tank whence the dissolved metals are conducted to the copper solution tank and thence to the precipitation tower as already described. The weakest wash solution is #5, this gathering strength each time the current passes through the leaching tank for urposes of washing the sands of undraiined metallic salts), wash solution #3 being the strongest in salts.

This progressive increase in the strength of` the wash solutions prevents an tindesirable weakening of the leaching solution with which the wash solutions mingle. The drawing likewise shows the liquid from the absorption tower in which are absorbed the fumes of the chloridizing hearths of the roasting furnace, as discharging into leachintensa ing solution jul-2. ylhe door` ot the liquids as here shown need not ot course loe strictly adhered to, any other method tor conservingP the desired strength ot'` the leaching solution telling within the contemplation ot my inyention.

'lhe several instrumentalities employed in my process, such as tanks, towers., tiiter presses, precipitation towers., roasting tur naoes, gas generators, and the like may loe raried at will, such Variation in no Wise adeeting the process so long as substantially the succession of step-s here outlined are adhered to.

ll-laving described my invention, what li claim is l. lin the recovery oit metallic copper and silver from a sullid ore otD said metals, the process ot subjecting a charge et the ore to a preliminary oxidizingl roast, then to la solo sequent roast in the presence ot salt, eulojecting the resulting calcine to the action oit water containing suitable proportions ot sul t'uric acid and saltthereloy leaching the rnetallic salts from the ore, subjectingu the resulting solution to the action ol sultureted hydrogen whereby the metals are precipi tated as sultids, and at the same time re generating the leaching solution, and split tingn the latter at the conclusion ot each cycle ot operations, tor the purpose set torth.

2. ln the recovery ot metallic copper and silver trom a sullid ore of said metals, the process ol subjecting a charge ot the ore to a preliminary oiridieing roast, then to a subsequent roast in the presence otb salt, subi ecting the resulting calcine to the action ot Water containing suitable proportions ot' sulturic acid and salt, thereby leaching the me tallic salts trom the ore, subjecting the resultingsolution to the action ot sulfureted hydrogen Whereloy the metals are precipitated as sullids and at the same time regenerating the leaching solution, and returning the major portion. of the regenerated leaching solution tor treating lresh charges ot ore.

ln testimony whereof l alllir my signature, in presence ot two Witnesses.

lllannnn Jenner, @Lavori B. Mannen.- 

